The coil-globule transition for poly(methyl methacrylate) has been studied in the mixed solvent tert-butyl alcohol+water system. Two polymeric samples having molecular weights M-w=2.55 x 10(6) and M-w = 4.73 x 10(6) were used. The contraction and expansion of the molecular chains were determined by viscometric measurements, The results were compared with light scattering data obtained recently for the same system. A smooth and continuous contraction was observed below the theta temperature (41.5 degrees C). The temperature dependence of [eta] can be represented by a master curve in alpha(eta)(3)\tau\M-w(1/2) vs \tau\M-w(1/2) plot, where alpha(eta)(3) = [ eta(T)]/[ eta(theta)] is a viscosity expansion factor and tau =(T - theta)/T is the reduced temperature. A comparison of the observed globular radius with a theory for contracted coil confirmed the coil-globule transition for this system. (C) 1998 American Institute of Physics. [S0021-9606(98)52443-9].